Are you getting an error like the one below?
Fatal error: Class ‘View’ not found in concrete5/concrete/core/libraries/loader.php on line 251
If so, you are probably wondering what on Earth is happening – and with reason. The problem is easy to fix, but quite hard to find. The error message turns out to be of absolutely no help in identifying the problem. While there may be different reasons for this problem, it seems to indicate that something related to the database is wrong – or at least that is often the case. Perhaps the database name, address, username or password is wrong. Or maybe your database is set up incorrectly.
No problems detected so far? Perhaps your PHP settings are incorrect, which would usually be the case if you are running on a local installation. You could create a simple script to test if PHP can connect to your database successfully, or you can jump straight into php.ini and check the path to the MySQL socket. Look for the following entries and verify that the paths are correct.
mysql.default_socket = /tmp/mysql.sock mysqli.default_socket = /tmp/mysql.sock pdo_mysql.default_socket = /tmp/mysql.sock
The paths above are paths for OS X 10.8 Mountain Lion, but they may differ depending on your system.
Hopefully this article has either directly solved your issues or at least helped narrowing down your search in order to identify the problem. If you know of any other reasons why this error occurs, then please leave a comment.